Abstract:
This experiment began in 1843. The site was possibly farmed since Roman times (i.e at least 1500 years). Map of 1623 shows field in arable use. 1839-1843 arable crops: turnips, barley, peas, wheat, oats. The soil is Clay-with-flint overlying chalk; see Avery & Catt, The Soil at Rothamsted (see reference list) for full details.

There have been 5 management regimes: 1) Continuous wheat 1844 onwards (occasional fallows). [field divided into 5 sections in 1926 to allow regular fallowing to control weeds and into 10 sections in 1968 to include rotations] 2) Potatoes-beans-wheat (1968-1979). 3) Fallow-wheat-wheat (1968-1981). 4) Fallow-potatoes-wheat-wheat-wheat (1982-1998). 5) Oats-maize-wheat-wheat-wheat (1996 onwards). Treatments (all regimes) are as follows: a) nil since 1852, b) FYM since 1844, c) FYM since 1885 plus N2 since 1968, d) FYM plus N4PK since 1968 (not continuous wheat), e) N0PK(Na)Mg since 1852, f) N1PK(Na)Mg since 1852, g) N2PK(Na)Mg since 1852, h) N3PK(Na)Mg since 1852, i) N4PK(Na)Mg since 1968, j) N5PK(Na)Mg since 1985, k) N6PK(Na)Mg since 1985. Other treatments receive NPK either singly or in various combinations. One treatment received rape cake then castor meal until 1988. (Na) - last applied 1973. FYM = 35 t/ha of farmyard manure: fresh it contains about 200-250 kgN/ha, 40 kgP/ha & 210 kgK/ha. P=35kgP/ha, K=90kgK/ha (P&K both annually). Mg = 35 kgMg/ha every 3rd year. N1, N2, N3, N4, N5, N6 = 48, 96, 144, 192, 240 & 288 kg N/ha/year as ammonium nitrate (N applied as ammonium sulphate to most plots until 1967). FYM and N will not be applied to oats in new oats-maize-wheat-wheat-wheat rotation. Of the 10 sections, 5 are in continuous wheat; straw has been incorporated in one since 1986, one has never received herbicides (fallowed every 5 years), one receives no fungicides. 5 sections are in the 5 year rotation. All sections have received chalk regularly since the 1950's.

Variables measured can be found in the Parameters section of this record. Frequency of measurements varies for each variable (Daily for weather, periodically for others, rarely for some). For detailed sampling methodology, see SOMNET site, or publications listed in references section on this record.

Description:
This url links to the GCTE-SOMNET home page where additional project information and methodology can be obtained. This site is currently in a datasharing phase of the network where actual data will become available shortly, at different levels of accessibility. Please follow this link for more information.

Quality
Width of smallest plot is 4 m Length of smallest plot is 23 m Width of largest plot is 6 m Length of largest plot is 320 m Slope: 2% on 2/5 of experiment . Shape: Uniform Details of direction of cultivation: Parallel to long-axis of plots Width of Bare Strip around plot: 1-1.5m paths. ... Width of Discard Strip around plot: 6.0m discard strip between sections. Details of homogeneity of the plots: Variability within plots: most plots are about 6.0m wide. Transects taken across several plots indicate that soil movement has occurred and that there is a gradient across the unplanted path extending about 1m into the plot. Soil and crop samples are therefore taken from within the central area (4.0m) and excluding a 1m strip on each side. Within this area, soil analysis shows that for C, N, pH Olsen P etc. the plots are reasonably uniform, c.v. about 10% (more for microbial biomass).

There are at least 0 replicates in the experiment. No true replication but the experiment was divided into 10 sections in 1968 (previously into 5 sections in 1926). Therefore, plots on sections 1 and 9 can be regarded as replicates. Sections 2,3,4,5 and 7 could be regarded as replicates over a five year period (i.e. the length of one rotation).

There are control plots described as follows: Nil inputs plot included which has received no inorganic fertilizers or organic manures since 1852. Nil plot does get chalk and pesticides on a regular basis. Also an area fenced off in 1882 and allowed to revert to natural woodland (see SOMNET entry on Broadbalk Wilderness).

Thorough scrutiny at point of entering onto electronic database (in 1995). Some soil and crop samples from archive have been reanalysed retrospectively; no unexplained discrepancies observed to date.